1. Field of the Invention
The present invention relates to an electro-hydraulic power steering apparatus formed integrally of a motor, a hydraulic pump driven by the motor, and a control device for controlling the motor.
2. Background Art
In the conventional electric pump, an electric motor is screwed coaxially with a bracket by inserting a plurality of securing bolts circumferentially into a mounting flange circumferentially provided on one side, and engaging them into the tapped holes formed on the lateral face on the other side of the bracket. By this fastening, a motor shaft serving as an output shaft of the electric motor is contacted with a pump shaft in a shaft center portion of the bracket, and coaxially connected by the coupling (e.g., refer to JP-A-2000-154791, paragraph [0030], FIG. 1)
In the conventional electric pump, a frame making up an outer shell of the electric motor was formed of die-cast aluminum, an iron core of a stator for the electric motor was press fit into an inner circumferential face of the frame, and the frame was screwed into a bracket on the pump from the hand of the frame (e.g., by six screws). Also, a bearing on the pump rotatably bearing a rotor of the electric motor is supported by an intermediate bracket that is a separate component from the frame, and the intermediate bracket is screwed into the frame from the hand of the pump (e.g., by four screws).
In the conventional apparatus as constituted in the above manner, the frame was screwed into the bracket on the pump from the hand of the frame, and the intermediate bracket was screwed into the frame from the hand of the pump, whereby right hand and left hand ways of screwing were required (i.e., clockwise and counterclockwise directions), resulting in a problem that the electric motor was assembled with difficulties. Also, since the iron core made of iron was press fit into the frame made of aluminum, the press fit iron core might be shaky due to a difference in the thermal expansion coefficient between the frame and the iron core. If the press fit interference was increased to prevent the shakiness, a greater residual stress was caused by press fitting, resulting in a problem that the motor performance was degraded. Also, since the mounting flange provided circumferentially on one side was formed integrally with the frame made of aluminum, no abutment face existed between the frame and the mounting flange, taking effect to reduce the water proofing portion. However, since the frame was made of aluminum, the outer shell was increased in size, resulting in a problem that the mounting was worsen.